Shearing line for edge-trimming and cutting metal sheets and plates

ABSTRACT

A shearing line for metal sheets and plates comprises opposite continuously driven straight-knife edge-trimming shears D1, D2 followed by crosscut shears moving with a rolling cut. The stepwise advancement of the sheets along the edge-trimming shears and through the crosscut shears may be reduced so as to cut any desired partial length.

United States Patent [72] Inventors Karl Wilhelm Greis Saint Ingbert-Saar; Everard Henri Sigal, Alschbach, Blieskastel-Saar, Germany [21 1 Appl. No. 808,829

[22] Filed Mar. 20, 1969 [45] Patented Jan. 19, 1971 [73] Assignee Moeller 8: Neumann G.m.b.l-l.

Ensheimer St a, Germany [32] Priority Mar. 20, 1968 [33] Germany [54] SHEARING LINE FOR EDGE-TRIMMING AND CUTTING METAL SHEETS AND PLATES 11 Claims, 10 Drawing Figs. [52] US. Cl. 83/208, 83/210, 83/241, 83/255, 83/282, 83/363, 83/367, 83/369 51 Im. Cl B 2 3d 31/0Q,

. B26d 5/26 [50] Field ofSearch 83/210, 213, 214, 208, 241, 255, 268, 282, 363, 364, 367,

[56] References Cited UNITED STATES PATENTS 1,812,122 6/1931 Streine 83/363X 1,986,685 1/1935 Soderberg 83/644 Primary Examiner-William S. Lawson Attorney-John J Dennemeyer ABSTRACT: A shearing line for metal sheets and plates comprises opposite continuously driven straight-knife edgetrimming shears D1, D2 followed by crosscut shears moving with a rolling cut. The stepwise advancement of the sheets along the edge-trimming shears and through the crosscut shears may be reduced so as to cut any desired partial length.

PATEN'TEDJAMQIQH Q G LES 5951 I SHEEMUFS PATENIEnJm-m sum 3 0P5 SHEARING LINE FOR EDGE-TRIMMING AND CUTTING METAL SHEETS AND PLATES This invention relates sa shearing line for edge-trimming and cutting metal sheets and plates in which two straight-knife edge-trimmingshears are mounted opposite each other inside the rolling train of the shearing line and are followed by crosscut shears. The oppositely mounted edge-trimming shears which provide a substantial reduction of the length of the shearing line have becomeknown by the term double side edge-trimming shears. The oppositely mounted edgetrimming shears will thus be called hereafter double side edgetrimming shears.

In front of the double sideedge-trimming shears the metal sheets have to be positioned only once and pass through the double edge-trimming shears under a single clamping action between pinch'rollers or in clamping carriages. by which they are advanced for intermittent edge trimming. it has been found that the mounting of the double side edge-trimming shears is not only practical, in new buildings. due to the shortening of the shearing line and the elimination of the double positioning devices'in front of the conventionally staggered edge-trimming shears but that also the production of the double side edge-trimming shears for metal sheets that are edge trimmed without intermittent action can become so high that one encounters a lack of time during the operation of the crosscut shears. Due to the saving of the adjustment time the production ofgthe double side edge-trimming shears may be pushed so highthat the substantially heavier and thus slower cutting crosscutshears, in front of which the sheets must be positioned again after a'free discharge and. are eventually marked, cannot absorb the increasedproduction of the double sideedge-trimmingshears.

it is an object of the invention to eliminate the drawback of the crosscut shears without having to resort to the help of a second crosscut shears in a parallel shearing line whichwould. be an obvious solution. k

in a shearing line of the, aforementionedtype wherein the feeding of the metal sheet is carried out by at least one pinch roller pair actuatedin accordance with the knife movements of the continuously driveriedgeetrimming shears the object of the invention is attained in that the crosscut shears or socailed rolling cut shears which has a curved knife executing a rolling or rocking movementis mounted such a short distance behind the edge-trimming, shears that the sheets are cut without a free discharge under the clamping action of the one or more pinch roller, pairs and the last feeding interval or distance may be shortened independently of the continuous drive of the edge-trimming shears.

in view of this novel'arrangement the production of the shearing lines is governed solely by the production of the double side edge-trimming shears and the operation of the cross- ,cut shears does not cause any delays. Due to the short distance i between the double side edge-trimmingshears and the crosscut shears the necessity of anew positioning of the sheets in front of thecrosscut shears is eliminated because the cross cutsare made while the sheet isunder the clamping action of the pinch rollers of the edge-trimming shears, and accordingly the cross cuts are made of necessity at right angle to the .trimmed sheet edges.

The feeding of the sheet by the pinch rollers provides also the means for substantially increasing through contact pressure on the sheet the friction coefficient between the rollers and the sheet so as to arrivethus at the shortest possible acceleration values for. the sheet feeding movement. This has a decisive effect in. passing the production of the double side edge-trimming shears through the crosscut shears.

Finally the selection of a rolling cut shears with a curved cutting knife provides the shortest possible work cycle based on the small strokes of thedrive crankshafts which become particularly small :whenthe curvature radiusof one of the knives is made at least SOmeters and preferably 60 meters.

Another novel. feature. of the; invention obtained incidentallyv is that the construction length ofzthe shearing line is reduced evenfurther. The control devices in front of the crosscut shears are also eliminated. This is already known for edge-trimming'and cutting sheet stacks (German Pat. No. 5 l6,6l l) but in this known arrangement the combination of double side edge-trimming shears and crossc ut shears into one unit have no relationship with the problem existing for heavy sheets or plates in shearing lines for obtaining the feeding of the increased production of a double side edge-trimming shears through a crosscut shears. This problem ceases to exist when by means of opposite edge-trimming shears sheet stacks are finish trimmed along their entire length with a single cutting stroke. Sheet stacks do not arrive in such a rapid sequence as the metal plates contained in a rolled slab.

in a double side edge-trimming shears the feeding for the sheets to be trimmed intermittently is normally derived from the continuous drive of the edge-trimming shears wherein the advancing distance is adjusted to the specific knife length of the edge-trimming shears. The last feeding distance of the pinch rollers can be shortened according to the invention independently of the continuous drive of the edge-trimming shears, so as to be able to cut sheet lengths that deviate from the normally fixed feeding distances or intervals for the purpose of cropping arbitrarily the front and rear sheet ends as well as in a controlled manner by the said signals of a length measuring device which may be adjusted to the desired sheet length run through after the cropping cut.

With respect to this point one of several possibilities is selected because one could also shorten all the feeding distances contained in the desired sheet length proportionately in such a way that the sheet length is always a total number multiple of the calculated and shortened feeding steps. However, with these processes-one would obtain especially in the case of short cutting lengths which lie only slightly above the unit or the double of the maximumfee'ding distance the first shortened feeding distances would become unsuitably small so that the lateral guiding of the forward trimmed sheet edges would not be optimal for astraight movement of the sheet.

The invention comprises furthermore a control for shortening the last feeding. distance of the drive rollers according to the measurement values of a length measuring device which are compared with previously set values of the desired sheet length and which stops the driving rollers when there is a zero comparison. For this purpose a control is provided having a device 10 started by an initial croppingcut of the crosscut shears T for producinga first signal proportional to a sheet length to be advanced thereafter in one or more steps, a preselector 62 for storing asecond signal L proportional to the desired partial length, and a first comparator 60 for generating an impulse for shutting down the pinch roller pairs 4,6 upon a zero comparison independently of the drive of the edge-trimming shears.

It is another object of the invention to avoid that the cross knives which are connected at the end of the trimming knives of the edge-trimmingshears do not bite a sufficient distance from the cross knife cutting edge of the penultimate cut and thus do not penetrate. This danger exists when the desired sheet length is only slightly larger than a multiple of the stationary or set feeding distance. if this may be seen from a preliminary calculation the control produces a shortening also of the penultimate feeding interval whereby the last feeding interval is brought at least to the size, e.g. to at least one sheet thickness at which'the cross knives definitely will bite and make a cut.

in order to produce a further saving of time the control provides an automatic start of the crosscut shears when the driving rollers are stopped, preferably at a point shortly before the stopping of the pinch rollers, so that the acceleration time of the crosscutshears may still overlap with the feeding of the sheet.

Conversely the feeding of the sheet should be started already before stopping the crosscut shears after anexecuted severing cut at the moment when the. returning cutting knife .reaches a certain level. lnthe case'of a crosscut shears with two crank drives staggered relativeto each other this is ob the invention a shearing line of short construction length. In

the drawing:

FIG. 1 is a side view of a double side edge-trimming shears and of a crosscut shears mounted in close proximity thereafter;

FIG. 2 a plan view of the shearing unit built into a rolling train;

FIG. 3 shows diagrammatic illustrations ae of the crank drive ofcrosscut shears with a rolling cut in five different positions of the upper knife;

FIG. 4 is an electrical switching diagram for the arbitrary and the controlled disengagement of the pinch rollers or sheet feeding means;

FIG. 5 shows in a and 1) two illustrations of a sheet with the references required for understanding the control according to the invention to set the desired sheet length; and

FIG. 6 is a block diagram of a control for shortening also a penultimate feeding distance.

Referring now to the drawings it will be seen that FIGS. 1 and 2 show a displaceable edge-trimming shears D1 mounted inside the shearing line with the rolling train rollers 2 and the stationary edge-trimming shears D2 which are disposed on opposite sides to provide double side edge-trimming shears. In the area of the double edge-trimming shears the sheets are clamped by pairs of pinch rollers 4 and 6 and moved forward absolutely along a straight edge according to which the continuously operating edge-trimming shears make their cuts.

Directly behind the double side edge-trimming shearsa crosscut shears T is mounted which presents behind the knife plane a pinch roller pair 8 for the purpose of pulling through in each instance the last sheet end after it has left the pinch rollers 6. At least the rolling train rollers inside the crosscut shears T are loose rollers. A sensing roller pair 10 in front of the knife plane of which one roller is driven serves to measure the traveling sheet length, as will be explained hereafter. The end stripping device 12 is of conventional construction. In order to feed the sheets after their rear ends have left the pinch roller pairs 4 still at right angle each edge-trimming shears is provided with brackets 14 carrying guide rollers 16.

The sheets are thus cut in the crosscut shears T under the clamping action by the feeding and guiding means 4, 6. 16 of the double side edge-trimming shears.

The crosscut shears T is a so-called rolling cut shears with an upper knife which is moved in a rolling or rocking cut and has a curved cutting edge.

The knife movements of such a known shears will be explained in greater detail hereafter with reference to FIG. 3. In this FIG. are shown diagrammatically the curved upper cutting knife 18, the stationary lower knife 20, as well as two crank rods 22, 24 connected at an interval from each other to the upper knife I8 and driven by crank pins 26, 28. The elements 18 and 20 could also function as knife supports.

FIG. 3a shows the starting position in which the staggered position of the crank drives may be seen.

When the crosscut shears is started the crank pins 26, 28 move in a counterclockwise direction indicated by the arrows. In FIG. 3c where the crank pin 26 is approximately in its lower dead center position the cut is half finished.

With regard to FIG. 3d the two crank rods 22. 24 are approximately in a reversed position. and in FIG. 3e the cut is completed, whereupon the crank pins 26.28, in a position according to 3a, are stopped.

An appropriate operation system of the double side edgetrimming shears-crosscut shears unit according to the invention is explained with reference to the switching diagram ac cording to FIG. 4. The power lines 32, 34 belong to an auxiliary control circuit, the pair of lines 36 are the circuit for operating the motors T of the crosscut shears, and the pair of lines 38 operated intermittently in derivation from the continuously driven edge-trimming shears DI and D2. This is obtained by means ofa control cam wheel 40 mounted on a crank shaft of the edge-trimming shears and rotating in the direction indicated and which is about to close a switch 41 over a sensing roller 42 during the return stroke of the knife of the edgetrimming shears. This causes a relay 44 to be energized which closes the switch 46 in circuit 38 and connects the motors Y of the feeding means. The switch 41 opens automatically under spring pressure when the cam shaft 40 releases the tracer 42.

In view of the fact that first the forward end of the sheet must be cropped provision is made that the feeding means which normally carry out a set advancing movement corresponding to the knife length of the edge-trimming shears may be arbitrarily shut down. This is obtained by a push bottom 48 whereby no current is passed to the relay 44 even in the case where the cam wheel 40 keeps the switch 41 closed. By pressing the push button 48 of one obtains thus not only the opening of switch 50 but also the closing of the switch 52 in the control circuit of a relay 54 which upon being energized closes the switch S6 in circuit 36. so that the motors T of the crosscut shears are connected. A holding contact (not shown), keeps the switch 52 closed and the switch 50 opened until a working cycle of the crosscut shears is finished.

When the first cropping cut is executed a length measurement must be made in order to advance an established sheet length into the crosscut shears. and this independently of the number of strokes the double side edge-trimming shears carry out.

Accordingly provision must be made that the feeding means can be shut down in a controlled manner according to the signal of a length measuring device.

Referring to FIG. 1 it may be seen that one of the sensing rollers 10 is connected to a pickup 58 which transmits counting pulses dependent on the number of revolutions and representing a first signal proportional to the sheet length which is advanced to a first comparator 60. Into the comparator 60 goes from a preselector 62 also the impulse sum as a second signal proportional to a desired cutting length. By comparing constantly in the comparator 60 the first signal with the set second signal an impulse is given by the comparator 60 over the line 64 to shut down the feeding means when the comparison is zero.

Reverting to the switching diagram according to FIG. 4 it is pointed out that the line 64 transmitting the stop pulse carries control current and is closed in the comparator 60 by a switch 66 when the value reaches zero of the nominal-actual value comparison, i.e. when the desired sheet length based on the preliminary setting is run off in the device 62. When the switch 66 is closed the relay 68 is energized, the switch 70 opened and the switch 72 closed which is in the loop 74 ofthe control line 76. The opening of switch 70 has the same effect as in the case of the push button switch 50, i.e. the feeding means are shut down independently of the drive of the edge-trimming shears. Upon closing of the switch 72 -as upon closing of the switch 52-the relay 54 is energized and the crosscut shears is automatically started by the stop pulse. Simultaneously the feeding drive is blocked due to the relay 44 which is without current.

In order that the length measurement commences exactly at the first cropping cut a branch line 78 leads from the control line 76 to a preliminary switching device 80 of the pickup 58. and it carries a voltage impulse when by pressing of the push button 48 for initiating the cropping cut the switch 52 in line 76 is closed. This voltage impulse causes in the preliminary switching device 80 that the pickup transmits the rotation signals emitted continuously by 'a sensing roller 10 as first signal during which the one or more subsequent distance effected by the cam wheel 40 to the first comparator 60.

The circuit is improved appropriately in the sense that the comparator 60 transmits shortly before the termination of the nominal-actual value comparison an impulse or a relay which delays the advancing means to a crawling speed in order that the sheets do not move on at the final shut down due to their proper inertia weight.

As described so far the control of the shearing line provides that in each instance the last advancing distance may be shortened independently of the continuous drive of the edgetrimming shears, thatis independently of the rotations of the cam wheel 40. In order to explain this procedure reference is made to FIG. 5a which shows a section of a sheet 81 which from the line 85 of a separation cut of the crosscut shears T is assumed to have anundetermined length. The out along line 85 may be initiated arbitrarily by pressing the push button 48 (FIG. 4). By means of the voltage impulse passing through line 78 to the device 80 the intermittent length measurement operation is released. The advancing distances V,, V V and V, run off successively.

The reference Lp designates the desired finished length of a sheet in which a multiple of V is aliquant so that the crosscut line 87 lies inside the subsequent advancing distance V,, which must be reduced by a distance Av, This is carried out by the nominal-actual value comparison in the first comparator 60 in which the actual value of the passed sheet length V1+V2 v..+v;+tvt av,riseaihpaiea"as first signal with the desired sheet length L as established second signal. Upon a zero comparison the advancing movement is shut down by closing of the switch 66 in the comparator 60 and the crosscut shears is actuated wherein circuitwise provision can be made to shut down the sheet feeding in a delayed manner through a crawling speed and to connect the crosscut shears within the scope of its inertia just before the sheet stops.

It may occur that a desired sheet length lies only slightly above a multiple of the advancing distance. In such a case it is not only difficult to move exactly the distance of the remaining small stretch after finishing the last complete advancing distance V, but there is also the danger that the cross knives of the double side edge-trimming shears D,, D, encounter too little meat and slide off when the remaining feeding distance lies between zero and the sheet thickness for example, to indicate a limit for the danger of a sliding off.

Such a case may be calculated ahead of time since one can determine and investigate for example continuously the differencebetween the second signal L,- and the first signal L, of the travelled sheet length to see when there is a difference Lp L which lies between a full advancing distance V and a value V sheet thickness d. In this respect reference is made to FIG. 5b where along the upper edge of the sheet 83 edge trimming cuts corresponding to the advancing distances V, to V, are marked along the line 89. It can be seen that with a desired sheet length L; after completion of the last full advancing movement V, only a residual advance V is necessary to cut off yet the small remaining edge piece 91. If V' is smaller than the sheet thickness d the mentioned difficulties arise and this independently of whether the severing cut is carried out by cross knives directly following the lengthwise cut or after the subsequent working cycle of the edge-trimming shears, at least as far as the difficulties of an advancing movement over small distances is concerned.

In the case where conditions according to FIG. 5b above are determined through calculations a control arrangement which is developed further within the scope of the invention and illustrated in FIG. 6 provides that the penultimate advancing step V, is shortened to the extent that V, V is divided into two partial advancing steps of which each is of such a length that the cross knives will positively cut in during the edge trimming cut and/or the advancing control including a delayed action before the shut down has enough time for providing the orderly procedure of the shut down process.-

At the lower sheet edge in FIG. 5b is indicated that when the condition:

is fulfilled the second preset signal L; is corrected by AV i.e. a shortened first partial advancement AV, s set which is followed while continuing the zero comparison in device 60 by the second partial advancement AV which initiates the crosscut and which are both sufficiently large. After the first partial advancement AV a shortened edge strip 93 is severed which is followed by a residual strip 97 in the double 4). shears before the crosscut along the line 95.

The control arrangement required for shortening also the penultimate feeding distance is shown in the embodiment of FIG. 6. It may be seen that the elements 10, 58, 60, 62, 64, 78, already mentioned as well as the actual feeding control 44, 46 and the crosscut control 68, 72, 54, 56 are enlarged by a combination of devices which is surrounded by the dash line 43.

In addition an impulse counter 45 for partial advancing lengths is shown which receives its impulses over line 47 from the pickup of the measuring rollers 10 and which emits over line 49 an impulse sum signal corresponding to the actually effected advancing step L The additional elements inside the line 43 comprise first a differential device 61 for the continuous indication of the difference L; -L,.,, (FIG. 5b) derived from the signals of the preselector62 and the pickup 58 as well as a second after-connected comparison device or a discriminator 63 for determining if at any time the condition:

is fulfilled, i.e. after a last feeding movement, e.g. V a too small feeding distance V' d remains. If this is the case an impulse travels over line 65 into the switch 67 and moves the switch 69 from the illustrated normal position assured by means of spring pressure or the like over to the contract contact 71. In the normal position of the switch 69 the control magnitude V corresponding to the full advancing length which is introduced according to FIG. 4 by the control wheel 40, 41 is transmitted over line 73 to a third comparison device 75 for the zero comparison V =V whereby over line 77 the normal advancing control 44, 46 for full advancing lengths is actuated. in front of the advancing device 40, 41 a line 84 leads also to a summer 86 in which the value d coming out of the preselector 88 is added to V. This sum V d goes into the second comparator 63.

In the position of switch 69 on contact 71 a preselector 79 for the control magnitude of the shortened first partial advancing length AV, is switched to the comparator 75. Since after each shut down of an advancing movement an impulse travels from the advancing control 44, 46 over the line 82 for canceling the impulse sum in the counter 45, the actual value V, of the sheet advance within an advancement step is constantly present. By comparing this value V, now with the value V, which is preset to about one half of a full advancing step V at 79 the third comparator 75 furnishes now a premature stopping impulse so that the edge-trimming shears separate only the edge strips 93.

Already soon after the partial advancing step AV, has started the difference L; L, in the devices 61 and 63 becomes smaller than V, i.e. the impulse travelling through line 65 is canceled, the switch 69 drops back into the normal position and the control stands at full advancing steps." However, it is now overcome by the zero comparison in the first comparator 60 which furnishes over line 64 at L,- L an impulse to the feeding control 44, 46 for shutting down residual advancement AV as well as to the crosscut shears control 68, 72, 54, 56 for releasing the crosscut.

The control according to FIG. 6 in connection with FIG. 5b has the purpose of determining from the difference L L, a last residual advancing step V which is too small, and to subsequently divide the remaining total advance up to reaching the desired sheet length into two partial advancing steps. Obviously still other ways lead to a solution of the object of providing for each finished length L; two final, approximately equal partial advancing steps. eg by determining through calculation whether a comparison of L with all possible n'time advancing steps produces a residual amount V which is smaller than a to small" amount d.

Furthermore the amount d has been defined as the sheet thickness. However, when the edge-trimming shears have no cross knives on the input side but only on the output side (British Pat. 991,343) where the problem of an unsure cross knife cut in case of a too small residual advancement V does not arise at all then d is chosen alone with the viewpoint of setting a suffieiently long last partial advancing step. By sufficiently long" an advancing step is understood during which the feeding motors have sufficient time to be purposely shut down from a high constant number of revolutions dependent on the distance-namely by a nominal actual value comparison, e.g. according to L,- L,,,-so that the desired advancing length is obtained precisely.

in this respect the special feeding control according to FIG. 6 is independent of whether the crosscut shears is a rolling cut shears or not and whether the sheets are advanced by pinch rollers or by other means. as long as the crosscut shears are arranged without free discharge closely behind the oppositely disposed edge-trimming shears.

We claim:

I. A shearing line for edge-trimming and cutting sheets and plates comprising:

a. a roller train;

b. a pair of continuously driven straight knife edge-trimming shears;

c. crosscut shears disposed adjacent said continuously driven straight knife edge-trimming shears;

d. at least one pair of pinch roller means for moving the sheets at intervals;

0. drive means for said continuously driven straight knife edge-trimming shears;

f. said at least one pair of pinch roller means operating in conjunction with said drive means whereby said at least one pair of roller means rotate within intervals between cutting strokes and are stopped during cutting strokes; and

. said crosscut shears being mounted at a short distance behind said continuously driven straight knife edgetrimming shears, whereby the sheets are cut without free discharge thereof under the clamping action of said at least one of said pinch roller means, wherein the feeding step of said at least one pair of pinch roller means may be shortened independently of the movement of said continuously driven straight knife edge-trimming shears when a desired sheet length is exceeded.

2. A shearing line according to claim 1 wherein said continuously driven straight knife edge-trimming shears is a rolling cut shears with a curved knife making a rolling movement.

3. A shearing line according to claim 1 further comprising control including a means started by an initial cropping cut of said crosscut shears T for producing a first signal L, proportional to a sheet length to be advanced thereafter in at least one step. a first presclector means (62) for storing a second signal (L to the desired partial length, and a first comparator means (60) for generating an impulse for stopping said at least one pair of pinch roller means upon a zero comparison independently of the drive of said continuously driven straight knife edge-trimming shears.

4. A shearing line according to claim 3 further including a plurality of cross knife means mounted at the entry side of said continuously driven straight knife edge-trimming shears for separating edge strips cut from the sheets, means for setting a last shortened sheet advancing step AV exceeding at least the sheet thickness (d) dependent upon the given finished length (L of the sheet while shortening the previous feeding distance (V to a partial feeding step AV also exceeding the sheet thickness (d).

5. A shearing line according to claim 4. including a differential means for determining the differences between said second signal (L and said first signal (L a second comparator means (63) for determining if the condition:

reff i lS fulfilled, wherein V is the preset feeding distance and d the presettable sheet thickness, and a changeover switch means (67) for temporarily disconnecting the control magnitude of the full feeding distance V from the feeding control and connecting a control magnitude corresponding to a shortened partial feeding step (AV and set in a second preselector (79), said magnitude being greater than the sheet thickness (d) wherein the temporary changeover switching is effected through an impulse from the second comparator (63) when the condition:

is fulfilled.

6. A shearing line according to claim 4 wherein said impulses generated by said first comparator for stopping said at least one pair of pinch roller means by a zero comparison in the first comparator (60) actuate automatically a cutting stroke of the crosscut shears (T), the drive of said at least one pair of pinch roller means being electrically blocked during the working cycle ofthe crosscut shears.

7. A shearing line according to claim 6 including impulses for releasing a cutting stroke of the crosscut shears (T) emitted by the first comparator (60) to that extent shortly before the zero comparison where in consideration of the acceleration time for the starting of the shears up to the start of the cut an overlapping ofsheet feeding and knife movement is possible.

8. A shearing line according to claim 6. including means for releasing the sheet feeding dependent on the movement of the cutting knife of the crosscut shears (T) before the stopping of the cutting drive at the moment when the moved cutting knife is positively free also of a sheet ofmaximum thickness.

9. A shearing line according to claim 8 for a crosscut shears having two crank drives for the moved cutting knives staggered relative to each other and, a contactor adjustable over the crank distance of a crank member for releasing the sheet feeding action.

10. A shearing line according to claim 1 wherein the feeding step of said at least one pair of pinch roller means may be shortened independently of the drive of said continuously driven straight knife edge-trimming shears when a desired sheet length is exceeded comprising a control including means started by an initial cropping cut of said crosscut shears (T) for producing a first signal (L proportional to a sheet length to be advanced thereafter in at least one step, a first preselector means (62) for storing a second signal (L proportional to the desired partial length, and a first comparator means (60) for generating an impulse for stopping said at least one pair of pinch roller means upon a zero comparison independently of the drive of said continuously driven straight knife edgetrimming shears, said control further including a means for setting a last shortened sheet advancing step Aw exceeding a preset value (d) while shortening the previous feeding distance (V to a penultimate partial feeding step (AV,) also exceeding the preset value (d) which represents a feeding step extended suffieiently for properly accelerating, decelerating and stopping the motors of the feeding device to precisely obtain the desired advancing length.

11. A shearing line according to claim 9, including a differential means for determining the differences between the second signal (L and the first signal (L a second comparator (63) for determining ifthe condition:

is fulfilled. wherein V is the preset feeding distance and d the temporary changeover switching is effected through an impreset value, and a changeover switch means (67) for tempulse from the second comparator (63) when the condition: porarily disconnecting the control magnitude of the full feeding distance V from the feeding control and connecting a con-' F m SV+d trol magnitude corresponding to a shortened partial feeding step (AV and set in a second preselector (79), said magfulfillednitude being greater than the preset value (d) wherein the 

1. A shearing line for edge-trimming and cutting sheets and plates comprising: a. a roller train; b. a pair of continuously driven straight knife edge-trimming shears; c. crosscut shears disposed adjacent said continuously driven straight knife edge-trimming shears; d. at least one pair of pinch roller means for moving the sheets at intervals; e. drive means for said continuously driven straight knife edgetrimming shears; f. said at least one pair of pinch roller means operating in conjunction with said drive means whereby said at least one pair of roller means rotate within intervals between cutting strokes and are stopped during cutting strokes; and g. said crosscut shears being mounted at a short distance behind said continuously driven straight knife edge-trimming shears, whereby the sheets are cut without free discharge thereof under the clamping action of said at least one of said pinch roller means, wherein the feeding step of said at least one pair of pinch roller means may be shortened independently of the movement of said continuously driven straight knife edgetrimming shears when a desired sheet length is exceeded.
 2. A shearing line according to claim 1 wherein said continuously driven straight knife edge-trimming shears is a rolling cut shears with a curved knife making a rolling movement.
 3. A shearing line according to claim 1 further comprising control including a means started by an initial cropping cut of said crosscut shears T for producing a first signal Leff proportional to a sheet length to be advanced thereafter in at least one step, a first preselector means (62) for storing a second signal (LF) to the desired partial length, and a first comparator means (60) for generating an impulse for stopping said at least one pair of pinch roller means upon a zero comparison independently of the drive of said continuously driven straight knife edge-trimming shears.
 4. A shearing line according to claim 3 further including a plurality of cross knife means mounted at the entry side of said continuously driven straight knife edge-trimming shears for separating edge strips cut from the sheets, means for setting a last shortened sheet advancing step Delta V2 exceeding at least the sheet thickness (d) dependent upon the given finished length (LF) of the sheet while shortening the previous feeding distance (V4) to a partial feeding step Delta V1 also exceeding the sheet thickness (d).
 5. A shearing line according to claim 4, including a differential means for determining the differences between said second signal (LF) and said first signal (Leff), a second comparator means (63) for determining if the condition:
 6. A shearing line according to claim 4 wherein said impulses generated by said first comparator for stopping said at least one pair of pinch roller means by a zero comparison in the first comparator (60) actuate automatically a cutting stroke of the crosscut shears (T), the drive of said at least one pair of pinch roller means being electrically blocked during the working cycle of the crosscut shears.
 7. A shearing line according to claim 6 including impulses for releasing a cutting stroke of the crosscut shears (T) emitted by the first comparator (60) to that extent shortlY before the zero comparison where in consideration of the acceleration time for the starting of the shears up to the start of the cut an overlapping of sheet feeding and knife movement is possible.
 8. A shearing line according to claim 6, including means for releasing the sheet feeding dependent on the movement of the cutting knife of the crosscut shears (T) before the stopping of the cutting drive at the moment when the moved cutting knife is positively free also of a sheet of maximum thickness.
 9. A shearing line according to claim 8 for a crosscut shears having two crank drives for the moved cutting knives staggered relative to each other and, a contactor adjustable over the crank distance of a crank member for releasing the sheet feeding action.
 10. A shearing line according to claim 1 wherein the feeding step of said at least one pair of pinch roller means may be shortened independently of the drive of said continuously driven straight knife edge-trimming shears when a desired sheet length is exceeded comprising a control including means started by an initial cropping cut of said crosscut shears (T) for producing a first signal (Leff) proportional to a sheet length to be advanced thereafter in at least one step, a first preselector means (62) for storing a second signal (LF) proportional to the desired partial length, and a first comparator means (60) for generating an impulse for stopping said at least one pair of pinch roller means upon a zero comparison independently of the drive of said continuously driven straight knife edge-trimming shears, said control further including a means for setting a last shortened sheet advancing step ( Delta V2) exceeding a preset value (d) while shortening the previous feeding distance (V4) to a penultimate partial feeding step ( Delta V1) also exceeding the preset value (d) which represents a feeding step extended sufficiently for properly accelerating, decelerating and stopping the motors of the feeding device to precisely obtain the desired advancing length.
 11. A shearing line according to claim 9, including a differential means for determining the differences between the second signal (LF) and the first signal (Leff), a second comparator (63) for determining if the condition: 